FAIR VALUE (Fair value measurement recurring) (Details) - USD ($) $ in Thousands	Mar. 31, 2021	Dec. 31, 2020
Assets
Equity securities with a readily determinable fair value	$ 20,543
Level 1
Assets
Securities available for sale	1,019	$ 2,026
Derivative assets	0	0
Liabilities
Derivative liabilities	0	0
Level 2
Assets
Securities available for sale	6,369,476	6,125,949
Derivative assets	23,991	44,102
Liabilities
Derivative liabilities	29,791	51,962
Level 3
Assets
Securities available for sale	0	0
Derivative assets	0	0
Liabilities
Derivative liabilities	0	0
Forward commitments \| Level 1
Assets
Derivative assets	0
Forward commitments \| Level 2
Assets
Derivative assets	1,213
Forward commitments \| Level 3
Assets
Derivative assets	0
U.S. treasuries
Assets
Securities available for sale	1,019	2,026
U.S. agencies
Assets
Securities available for sale	212,292	166,779
Obligations of states and political subdivisions
Assets
Securities available for sale	1,737,989	1,635,227
Commercial mortgage-backed securities - agency
Assets
Securities available for sale	122,230	174,153
Commercial mortgage-backed securities - non-agency
Assets
Securities available for sale	307,774	252,767
Asset-backed securities
Assets
Securities available for sale	1,028,213	1,069,266
Corporate bonds
Assets
Securities available for sale	3,790	3,742
Recurring Basis
Assets
Equity securities with a readily determinable fair value	20,543	19,629
Total assets at fair value	6,397,556	6,173,904
Liabilities
Total liabilities at fair value	29,795	52,659
Recurring Basis \| Level 1
Assets
Equity securities with a readily determinable fair value	0	0
Total assets at fair value	1,019	2,026
Liabilities
Total liabilities at fair value	0	0
Recurring Basis \| Level 2
Assets
Equity securities with a readily determinable fair value	20,543	19,629
Total assets at fair value	6,394,680	6,170,051
Liabilities
Total liabilities at fair value	29,795	52,659
Recurring Basis \| Level 3
Assets
Equity securities with a readily determinable fair value	0	0
Total assets at fair value	1,857	1,827
Liabilities
Total liabilities at fair value	0	0
Recurring Basis \| Derivative financial instruments
Assets
Derivative assets	23,991	44,102
Liabilities
Derivative liabilities	29,791	51,962
Recurring Basis \| Derivative financial instruments \| Level 1
Assets
Derivative assets	0	0
Liabilities
Derivative liabilities	0	0
Recurring Basis \| Derivative financial instruments \| Level 2
Assets
Derivative assets	23,991	44,102
Liabilities
Derivative liabilities	29,791	51,962
Recurring Basis \| Derivative financial instruments \| Level 3
Assets
Derivative assets	0	0
Liabilities
Derivative liabilities	0	0
Recurring Basis \| Interest rate lock commitments
Assets
Derivative assets	1,857	1,827
Recurring Basis \| Interest rate lock commitments \| Level 1
Assets
Derivative assets	0	0
Recurring Basis \| Interest rate lock commitments \| Level 2
Assets
Derivative assets	0	0
Recurring Basis \| Interest rate lock commitments \| Level 3
Assets
Derivative assets	1,857	1,827
Recurring Basis \| Forward commitments
Assets
Derivative assets	1,213
Liabilities
Derivative liabilities	4	697
Recurring Basis \| Forward commitments \| Level 1
Assets
Derivative assets	0
Liabilities
Derivative liabilities	0	0
Recurring Basis \| Forward commitments \| Level 2
Assets
Derivative assets	1,213
Liabilities
Derivative liabilities	4	697
Recurring Basis \| Forward commitments \| Level 3
Assets
Derivative assets	0
Liabilities
Derivative liabilities	0	0
Recurring Basis \| U.S. treasuries
Assets
Securities available for sale	1,019	2,026
Recurring Basis \| U.S. treasuries \| Level 1
Assets
Securities available for sale	1,019	2,026
Recurring Basis \| U.S. treasuries \| Level 2
Assets
Securities available for sale	0	0
Recurring Basis \| U.S. treasuries \| Level 3
Assets
Securities available for sale	0	0
Recurring Basis \| U.S. agencies
Assets
Securities available for sale	212,292	166,779
Recurring Basis \| U.S. agencies \| Level 1
Assets
Securities available for sale	0	0
Recurring Basis \| U.S. agencies \| Level 2
Assets
Securities available for sale	212,292	166,779
Recurring Basis \| U.S. agencies \| Level 3
Assets
Securities available for sale	0	0
Recurring Basis \| Obligations of states and political subdivisions
Assets
Securities available for sale	1,737,989	1,635,227
Recurring Basis \| Obligations of states and political subdivisions \| Level 1
Assets
Securities available for sale	0	0
Recurring Basis \| Obligations of states and political subdivisions \| Level 2
Assets
Securities available for sale	1,737,989	1,635,227
Recurring Basis \| Obligations of states and political subdivisions \| Level 3
Assets
Securities available for sale	0	0
Recurring Basis \| Mortgage-backed securities - agency
Assets
Securities available for sale	1,432,929	1,355,270
Recurring Basis \| Mortgage-backed securities - agency \| Level 1
Assets
Securities available for sale	0	0
Recurring Basis \| Mortgage-backed securities - agency \| Level 2
Assets
Securities available for sale	1,432,929	1,355,270
Recurring Basis \| Mortgage-backed securities - agency \| Level 3
Assets
Securities available for sale	0	0
Recurring Basis \| Mortgage-backed securities - non-agency
Assets
Securities available for sale	1,503,716	1,449,116
Recurring Basis \| Mortgage-backed securities - non-agency \| Level 1
Assets
Securities available for sale	0	0
Recurring Basis \| Mortgage-backed securities - non-agency \| Level 2
Assets
Securities available for sale	1,503,716	1,449,116
Recurring Basis \| Mortgage-backed securities - non-agency \| Level 3
Assets
Securities available for sale	0	0
Recurring Basis \| Commercial mortgage-backed securities - agency
Assets
Securities available for sale	122,230	174,153
Recurring Basis \| Commercial mortgage-backed securities - agency \| Level 1
Assets
Securities available for sale	0	0
Recurring Basis \| Commercial mortgage-backed securities - agency \| Level 2
Assets
Securities available for sale	122,230	174,153
Recurring Basis \| Commercial mortgage-backed securities - agency \| Level 3
Assets
Securities available for sale	0	0
Recurring Basis \| Commercial mortgage-backed securities - non-agency
Assets
Securities available for sale	307,774	252,767
Recurring Basis \| Commercial mortgage-backed securities - non-agency \| Level 1
Assets
Securities available for sale	0	0
Recurring Basis \| Commercial mortgage-backed securities - non-agency \| Level 2
Assets
Securities available for sale	307,774	252,767
Recurring Basis \| Commercial mortgage-backed securities - non-agency \| Level 3
Assets
Securities available for sale	0	0
Recurring Basis \| Asset-backed securities
Assets
Securities available for sale	1,028,213	1,069,266
Recurring Basis \| Asset-backed securities \| Level 1
Assets
Securities available for sale	0	0
Recurring Basis \| Asset-backed securities \| Level 2
Assets
Securities available for sale	1,028,213	1,069,266
Recurring Basis \| Asset-backed securities \| Level 3
Assets
Securities available for sale	0	0
Recurring Basis \| Corporate bonds
Assets
Securities available for sale	3,790	3,742
Recurring Basis \| Corporate bonds \| Level 1
Assets
Securities available for sale	0	0
Recurring Basis \| Corporate bonds \| Level 2
Assets
Securities available for sale	3,790	3,742
Recurring Basis \| Corporate bonds \| Level 3
Assets
Securities available for sale	$ 0	$ 0

Fair value portion of probable future economic benefits obtained or controlled by an entity as a result of past transactions or events.

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Amount of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

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